Take 100 ml of distilled water in two polythene bottles. (This prevent heat loss.) Note the temperature of water in both bottles. Add about 5 gm of potassium nitrate (KNO3) to one bottle stir well. Note temperature of the solution. Add 5 gm of NaOH to the other bottle. Note the solution temperature. What do you observe in both the cases ? What inferences can you draw ?
Ans. At the start, temperature of distilled water in two bottles was suppose 60oC. When we add KNO3 to one of the bottles, temperature of solution falls down to 50oC, this is because there is absorption of heat during the reaction.
When we add NaOH to other bottle, there is rise in temperature as there is evolution of heat during this reaction.